1. Field of the Invention
The invention is directed to a hose arrangement for a seal-less centrifuge.
2. Discussion of the Prior Art
For the separation of cell suspensions such as blood, there are utilized seal-less centrifuges such as those described, for example, in German Patent DE A 32 42 541. In this apparatus, the blood is led via a hose arrangement to the centrifuge in which it is separated into its component parts which are then led out through different channels in the hose arrangement. Herein the hose arrangement is stationery at its input end and runs from this input end in a loop around the rotor of the centrifuge and exits at its other end into the separation chamber of the centrifuge. If no avoiding steps are taken a twisting occurs and thus a ripping of the hose arrangement between the fixed end on the one hand and the other end rotating with the speed of the centrifuge. To avoid this the hose arrangement, while being lead around the rotating centrifuge chamber is subjected to a constant de-twisting treatment, that is to say, the hose does not any longer rotate around the separation chamber but rather continuously rotates about its own hose axis in a manner counter to the twisting rotation.
A problem in such hose arrangements is therefore their relative movement which leads to frictional and shearing forces in the hose arrangements. This can have the result on the one hand of a sharp bending of the hose arrangement in its end region and on the other hand to a mutual wearing down of the hose components. In order to reduce the friction and to improve the absorption of the gravitational forces, relatively hard materials have been utilized for the hose arrangement. As a result of the self rotation resulting from de-twisting treatment, the hose arrangement hits against the centrifuge during each rotation which leads to a strong and highly undesired sound generation. On the other hand, if the hose material is made soft, the noise generation is reduced but the wearing down of the hose material increases so that the hose material can eventually wear out.
In order to solve the bending problem, suggestions have been made in U.S. Pat. No. 4,109,852, U.S. Pat. No. 4,164,318 and European published application No. 1 129 90, which propose that the flexible casings at the hose ends should be surrounded by a multi-lumina hose arrangement which serves a plurality of input and output channels. Such individual portions are relatively complex to produce and their installation as well as its use as a disposable article are very expensive. Furthermore, the installation of this hose requires higher service requirements.
To the problem of frictional wear, European Patent Publication EP 2 60 034 offers a flexible hose with a woven abrasion guard. If such a guard is axially stretched, it is pulled together radially and constricts itself on the hose. Such a frictional guard is complex to produce and is substantially unsuited as a disposable article for medical purposes.
Furthermore, it is established that hose leads or complete casings are complex to produce. Additional components such as bearings and like are required in order to assure proper functioning. On the other hand, if the hose itself has no guide parts, a rounded edge on the hose ends can prevent excessive bending, it cannot prevent frictional wear since the hose slides on this rounded end as has been shown in the previous invention.
In U.S. Pat. No. 4,299,256, there is provided a hose arrangement with one or several lumina of at least one polymeric material suitable for a seal-less centrifuge, which is made out of a layer of PVC with a small proportion of silicone oil and an inner layer of a different synthetic material which is silicone oil free. On the one hand, the provision of synthetic material filled with silicone oil is expensive and on the other hand leads to an undesirably soft outer material which does not provide the centrifuge hose with the necessary stability during high centrifuge speeds.